Carp lockdown could flood Chicago, water district warns

(Crain's) -- Closing Chicago-area river locks to keep Asian carp out of Lake Michigan could cause widespread flooding for 5 million residents and thousands of businesses, Chicago's water treatment agency warned the U.S. Supreme Court Tuesday.

Michigan and other Great Lakes states are seeking an emergency order from the nation's highest court to shut down immediately locks on the waterway system after it became evident last month that an underwater electronic barrier built by the federal government may not keep the voracious fish at bay.

While the states argued that the benefits of stopping the predatory invasive fish outweighed the "temporary" economic harm of stopping barge traffic through Chicago, the Metropolitan Water Reclamation District of Greater Chicago said in its filing that the court "should include on the scale a weighty item omitted by Michigan: the potentially disastrous effects of flooding and impacts on public safety and health in the Chicago area."

The MWRD is a defendant in the case, along with the state of Illinois, because it owns the locks on the 76.3 miles of canals and waterways built to reverse the flow of the Chicago River, preventing pollution from reaching Lake Michigan and sullying the region's main drinking water supply.

The locks and the electronic barrier are operated by the Army Corps of Engineers.

To prevent flooding during heavy storms, the locks are opened to let storm water flow in the opposite direction to Lake Michigan.

While there have been only 10 such reversals in the last decade, the MWRD noted, five of those have been in the last 16 months.

Despite shared concerns about Asian carp, the state of Illinois weighed in Tuesday against closing the locks, citing the economic harm of disrupting hundreds of jobs and billions of dollars of bulk chemicals and materials carried annually by barge.